. . . So I'd have ONE wallet somewhere, then attach different bitcoin addresses to it? . . .
Exactly.
If that's best practice, I'll do it, and yes, I believe in privacy, although I am not super paranoid. But payments to a particular cause I believe in, payment for filesharing activities and whatever else I want to do in the future is nothing that my bank (and whoever accesses their records) needs to know about.
Because the blockchain (which stores all transaction history since the beginning of bitcoin's existence) is a publicly shared file, if you know a bitcoin address, you can see all transactions that have ever been sent to or from that address.
You can see here that the person who has the bitcoin address of 1ntp98QCoiMxLnn3iSjxWdff1cPMGnPAR likes to play SatoshiDice:
http://blockchain.info/address/1ntp98QCoiMxLnn3iSjxWdff1cPMGnPARYou can see a complete list of all the transactions they have ever sent or received from the 1ntp98QCoiMxLnn3iSjxWdff1cPMGnPAR address. Since you and I don't know who owns that address, they have some anonymity.
If you give me a bitcoin address so that I can send you some money, and then give that same address to everyone else who sends you money, then I will be able to tell exactly how much bitcoin you have received and how much of it you have spent so far. If I know the bitcoin addresses of any of the people who are sending you bitcoins, then I'd know who was sending it and how much they sent.
With some effort bitcoin addresses can still often be linked together, so if true anonymity/privacy are really important to you, you'll want to learn a bit more about how bitcoin creates transactions and how to avoid having a transaction link multiple addresses of yours together. But the simple action of having a separate bitcoin address for each transaction where you receive bitcoins goes a long way toward maintaining a reasonable amount of anonymity from casual inspection of your address/transactions.
. . . There is simply no telling how long the client will need. Does anyone keep an eye on the situation with this, or actually care? Or did you all set up your clients years ago and shrug at what's going on with newbies? I realize that not much can be done, but if this is just going to get worse in the future, then it's untenable . . .
Obviously you are neither the first person to notice the issue, nor the first person to mention it. I suspect that nearly EVERY TIME someone installs the Bitcoin-Qt client without first understanding what they are about to undertake, the next thing they do is come to the forum to complain about how long it takes. Certainly there are people looking into ways to improve on this. One of the more promising efforts underway involves pruning unneeded information from the blockchain to significantly reduce it's size. See these discussions for more technical information:
https://bitcointalk.org/index.php?topic=88208.0https://bitcointalk.org/index.php?topic=129861.0https://bitcointalk.org/index.php?topic=119525.0